1. Field of the Invention
The Present invention relates to a communication system suitable for use in communication of control information between the camera and lens assemblies of, for example, an interchangeable-lens type camera system.
2. Description of the Related Art
In recent years, imaging systems such as camera systems and video camera systems have been remarkably developing, and various kinds of imaging systems which have a variety of functions and which allow interchangeable lens assemblies to be used with a camera assembly have been available.
In such an imaging system, a camera assembly such as a video camera assembly (hereinafter referred to simply as a "camera assembly") obtains from an interchangeable lens assembly specific information indicative of various characteristics and control information relating to the interchangeable lens assembly. The camera assembly in turn transmits predetermined control information to the lens assembly on the basis of the specific information so as to provide various kinds of control such as auto-focus (AF), auto-exposure (AE) and auto-zoom (AZ).
Transmission of the above-described control information and characteristics information is commonly realized by the communication performed between the camera and lens assemblies.
As is known, such an interchangeable-lens type imaging system is constructed of camera and lens assemblies which functionally differ from each other, and its total function is determined by a combination of the functions of the camera assembly and those of the lens assembly.
FIGS. 1(a) and 1(b) are schematic views showing system arrangements each provided by a combination of camera and lens assemblies in a camera system of the above-described type. A case where either of camera assemblies A and B having different functions is, as shown in FIG. 1(a), combined with either of lens assemblies C and D having different functions will be considered below.
It is assumed, as shown in FIG. 1(b), that the camera assembly A is capable of controlling an AF block A-AF for providing an AF function, an AE block A-AE for providing an AE function, an AZ block A-AZ for providing an AZ function and that the camera assembly B is capable of controlling only an AE block B-AE for providing an AE function.
It is also assumed that the lens assembly C includes an AF block C-AF, an AE block C-AE and an AZ block C-AZ and can selectively perform their functions. Further, it is assumed that the lens assembly D includes an AF block D-AF and an AE block D-AE and can selectively perform their functions.
In a first combination in which the camera assembly A and the lens assembly C are connected to each other by a serial communication line DL, the AF, AE and AZ functions can be performed. In a second combination in which the camera assembly A and the lens assembly D are connected to each other by the serial communication line DL, the AF and AE functions can be performed. If the camera assembly B is applied to either of the first and second combinations, only the AE function can be performed.
To assure reliable compatibility with respect to lens assemblies having different functions, as can be seen from the examples shown in FIGS. 1(a) and 1(b), control information based on a common format and detection information indicative of the driven state of each element needs to be communicated between the camera assembly A or B and the lens assembly C or D over the communication line DL. To achieve such communication, an appropriate common format is needed.